Processes of continuous chemical nickel plating



Feb. 3, 1959 2,872,354

PROCESSES OE CONTINUOUS CHEMICAL NICKEL PLATINO w. G. LEE

Original Filed Dec. 3l. 1954 2,872,354 PROCESSES OF CONTINUOUS CHEMICAL NICKEL PLATING Warren G. Lee, East Chicago, Ind., assig'nor to General American Transportation Corporation, Chicago, Ill., a

corporation of New York Original application December 31, 1954, Serial No. 479,040. Divided and this application March 26, 1956, Serial No. 573,789

7 Claims. (Cl. 117-130) v The present invention relates to processes of continuous nickel plating of catalytic materials; and it is the general object of the invention to provide an improved process of the general character of that disclosed in U. S. Patent No. 2,717,218, granted on September 6, 1955, to Paul Talmey and William J. Cr'ehan. This application is a division of the copending application of Paul Talmey, Gregoire Gutzeit and Donald E. Metheny, Serial No. 479,040, tiled December 3l, 1 954, no'w abandoned, which application was originally filed, through error and without any deceptive intention, jointly by: Paul Talmey, Gregoire Gutzeit, Donald E. Metheny and Warren G.

` Lee.

The chemical nickel plating of a catalytic material employing an aqueous bath of the nickel cation-hypophosphite anion type is based upon the catalytic reduction of nickel cations to metallic nickel andthe corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas Val; the catalytic surface. The reactions take place when the body of catalytic material is immersed in the plating bath, and the exterior surface of the body of catalytic material is coated with nickel. The following elements are catalytic for the oxidation of hypophosphite anions and thus may be directly nickel plated: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following elements are examples of materials which may be nickel plated by virtue ofan initial displacement deposition of nickel thereon either directly or through a galvanic effect: copper, silver, gold, beryllium, germanium, aluminum, carbon, vanadium, molybdenum, tungsten, chromium, selenium, titanium and uranium. The following elements are examples of non-catalytic materials which ordinarily may not be nickel plated: bismuth, cadmium, tin, lead and zinc. The activity of the catalytic materials varies considerably and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel and palladium. The chemical nickel plating process is autocatalyticv since both the original surface of the body being plated and the nickel metal that is deposited on the surface thereof are catalytic. As time proceeds, the anions, as contrasted with the cations of the nickel salt that is dissolved in the plating bath, combine with the hydrogen cations to form an acid, which, in turn, lowers the pH of the plating bath.

In the continuous plating process disclosed in the Talmey and Crehan patent, the plating bath is regenerated continuously by the addition thereto of soluble nickelcontaining and hypophosphite-containing reagents, as well as an alkalizing reagent for pH control; which regeneration of the plating bath during the plating of the catalytic material maintains not only the desired nickel cation concentration and hypophosphite anion concentration, but also preserves the most advantageous pH of the plating bath to assure a high plating rate. The continuous nickel plating process and system disclosed' in this patent involves a plating chamber and a reservoir; and in the arrangement the plating solution is circulated from the reservoir to the plating chamber and back to the reservoir, the plating solution being heated to a relatively high temperature slightly below the boiling point thereof after with- United States Patent O pH adjusted to 4.6 with NaOH.

ice

drawal from the reservoir and before introduction into the plating chamber, and the plating solution being cooled to a relatively low temperature well below the boiling point thereof after withdrawal from the plating chamber and before return into the reservoir. Of course, the catalytic body or bodies are plated by immersion in the plating solution in the plating chamber, while the plating solution is regenerated in the reservoir by the addition of the previously mentioned reagents thereto in the reservoir. The catalytic body is subsequently withdrawn from the plating solution in the plating chamber after a time interval corresponding to the thickness of the nickel plating thereon that is desired.

A number of suitable aqueous chemical nickel plating baths of the nickel cation-hypophosphite anion type that may be employed in the continuous nickel plating system of the Talmey and Crehan patent are disclosed in U. S. Patent No. 2,658,841, granted on November l0, 1953, to Gregoire Gutzeit and Abraham Krieg and in U. S. Patent No. 2,658,842, granted on November 10, 1953, to Gregoire Gutzeit and Ernest I. Ramirez and in the copending applications of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Serial No. 478,492, iled December 29, 1954; Serial No. 479,088, tiled December 31, 1954, now Patent No. 2,822,293, and Serial No. 569,815, tiled March 6, 1956, now Patent No. 2,822,294. A plating bath of these types fundamentally comprises an aqueous solution of nickel ions and hypophosphite ions; and such a bath may comprise an absolute concentration of hypophosphite ions in the range 0.15 to 1.20 moles/liter, a ratio between nickel ions and hyphosphite ions in the range 0.25 to 1.60, and an initial pH in the approximate range 4 to 7. In the continuous' plating system, the plating baths disclosed in the Gutzeit, Talmey and Lee applications are preferred, both from the standpoint of economy and of performance; a preferred bath of this type essentially comprises an aqueous solution of nickel ions and hypophosphite ions and lactic ions and propionic ions, the absolute concentration of hypophosphite ions being in the range 0.15 to 1.20 moles/liter, the ratio between nickel ions and hypophosphite ions being in the range 0.25 to 1.60, the absolute concentration of lactic ions being in the range 0.25 to 0.60 mole/liter, the absolute concentration of propionic ions being in the range 0.025 to 0.060 mole/liter, and the bath having an initial pH in the range 4.4 to 5.6; and four typical examples of such aqueous plating' baths are as follows:

Bath l Nickel ions (as nickel sulfate) 0.08 m. p. l. Hypophosphite ions (as sodium hypophosphite) 0.230 m. p. l. Lactic acid 0.30 to 0.40 m. p. l. Lead sulfide (stabilizer) l p. p. m. Pb++. pH adjusted to 4.6 with NaOH.

Bath Il Nickel ions (as nickel sulfate) 0.07 to 0.08 rn. p. l. Hypophosphite ions (as sodium hy-V pophosphite) 0.225 m. p. l. Lactic acid 0.30 to 0.40 n1. p. l. Propionic acid 0.03 m. p. l. Lead suliide (stabilizer) l p. p. m. Pb++. pH adjusted to 4.6 with NaOH.

Bath III Nickel ions (as nickel sulfate) 0.08 m. p. l. vI-lypophosphite ions (as sodium hypophosphite) 0.225 m. p. l. Lactic acid 0.20 m. p. l. Succinic acid 0.06 m. p. l. Lead sulfide (stabilizer) 1 p. p. rn. Pb++,'

Lead sulfide (stabilizer) pH adjusted to 4.6 with NaOH.

l-p. p. rn. Pb++.

In addition, each of the Baths I, Il, III and IV contains a high-temperature stable, chemically inert, wetting agentof any suitable type; and in these baths the function of the organic additives (inalic acid, lactic acid, succinic acid and proponic acid) is three-fold, as they act as: (l) buffers; (2) exaltants (plating rate boosters); (3) complexing agents (to .prevent precipitation of nickel phosphite at high concentrations 'of HPOfions).

Of these organic additives, lactic acid combines the three effects named, succinic and propionic acids function principally as eXaltants, while malic acid functions mainly asa complexing agent.

In the formulation of any one of these plating baths, an aqueous solution is prepared of the ingredients named; the nickel cations may be derived from nickel sulfate. nickel chloride, etc., or various combinations thereof; the hypophosphite anions may be derived from sodium hypophosphite, potassium hypophosphite, etc., or various combinations thereof; the other additives are introduced into the bath normally as the acids, or as the soluble salts thereof, etc.; and the desired pH of the bath *is established by the eventual introduction thereinto of an acid or a base, as required, sulfuric acid and sodium hydroxide being recommended as a matter ofeconomy vand simplicity. Y

VYIn the compositions of the various plating baths, the termsfcation, anionf and ion, as employed, include the total quantity of the corresponding elements that are present in the plating bath, i. e., both the undissociated and dissociated material. In other words, 100% dissociation is assumed when the terms noted are used in connection with molar ratios and concentrations in the plating bath.

In the operation of the continuous plating system disclosed in the Talmey and Crehan patent, the whole body of plating solution, as a matter of volume, is continuously circulated from the reservoir to the plating chamber and back to the reservoir to constitute what may be termed a cycle of circulation; and continuous regeneration thereof is accomplished in the reservoir by the continuous introduction thereinto of the reagents previously mentioned. Now after the whole body of plating solution has been used in production plating in a plurality of cycles of circulation, with the requiredk regeneration thereof, its content in phosphite anions builds-up to a point where even the presence of relatively large quantities of complexing agents (necessarily rather weak complexing agents) cannot prevent the precipitation of nickel phosphite therein. This point is reached when the phosphite concentration attains 0.7 to 1.5 m. p. l., depending on the particular bath composition. The nickel phosphite'prccipitate in the plating solution forms a 'suspensoid whose semi-colloidal particles causes roughness of the plating on the catalytic bodies undergoing the plating operatio-n, and also act as nuclei for thermal catalytic decomposition of the whole body ot plating solution, i. e., the formation of black precipitate therethrough. When this point is reached, the whole body of plating solution may be termed depleted and has to be replaced Wtih a freshly prepared'body of plating solution in order to continuef'satisfactory plating of the catalytic bodies in the plating chamber. l

A depleted plating bath may have, for instance, the following approximate composition:

M. p. l. Nickel ions 0.07-0.08 Hypophosphite ions 0.22- 0.24 Phosphite ions 0.70- Sulfate ions 0.65-0.70 Lactic ions 0.20-0.40 Sodium ions q s.

Typical examples of a .few depleted plating baths of the type previously described were found to have the following compositions:

Depleted bath IA M. p. l.

Ni Aions 0.07 NaHZ'POZ 0.22 Nazi-1F03 0.80 Lactic acid 0.30

VDepleled bath IIA Ni ions 0.07 NaHzpOg NazHPOS 0.80 Lactic acid 0.30 Propionic acid 0.03

Depleted'balhIII-A NiV ions 0.084

NaH2PO2 Na2HPO3 Lacticv acid 0.20 Succinic acid 0.06

Depleted' bath IVA Nijions Y 0.068 NaH2PO2 v l Y NH2HPO3 Malic acid 0.06 Lactic acid 0.2025 Succinic acid 0.20

Depleted bath IVB Ni ions 0.07 NaH-POZ 0.20 Na2HPO3 0.86 Malic acid 0.06 Lactic acid 0.20 Succinic acid 0.20

While theregeneration: of the plating solution in the continuousplating process as disclosed in the Talmey and Crehan patent, and involving the continuous addition thereto of the reagents mentioned, contributes very substantially to economical industrial plating operation, 1t is apparent that this regeneration of the plating solu t1on does not proceed as far as is desirable in order to achieve maximum economy, sinceit will be observed from the compositions of the foregoing depleted plating baths that there are substantial values therein that might be further utilized.

Accordingly, it is another object of the invention to provide a continuous chemical nickel plating process of the character described that involves regeneration of the plating baths, not only by the addition thereto of nickelcontaining and hypophosphite-containing and alkalizing reagents, but also by the removal therefrom of phosphite ions, whereby depleted plating baths may be restored for further use.

A further object 4of the invention is to provide an improved process of restoring a depleted chemical nickel plating bath so that it may be employed for further use in the plating of catalytic bodies, which involves not only theremoval of'phosphite ions therefrom, but also the removal of other ions thathave been built-up therein as a consequence of the additions thereto of the reagents A. still further object of the invention is to provide an improved process of restoring a depleted chemical nickel plating bath so that it may be employed for further pse 1n the plating of catalytic bodies, which does not introduce any substantial foreign ions thereinto and which effects the recovery of tho valuable nickel cations, hypophosphite anions and organic additives therein.

The present invention is predicated upon the discovery that a depleted chemical nickel plating bath may be restored for further satisfactory use in a continuous chemical nickel plating system of the character described, by proper treatment of the depleted plating bath to remove therefrom phosphite anions and other ions that have been built-up therein by the addition of the makeup reagents, without the introduction of foreign ions, so that the resulting aqueous solution fundamentally containing nickel cations, hypophosphite anions and organic additives may then be directly restored merely by adding thereto nickel-containing hypophosphite-containing and acidifying or alkalizing reagents.

Still further features of the invention pertain to the particular arrangement of the steps of the process, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and principle of operation, together with further objects and advantages thereof, Vwill best be understood by reference to the following specification taken in connection with the accompanying drawing, in which the single figure is a diagrammatic illustration of a continuous nickelV plating system in which the process of the present invention may be carried out.

Referring now to the drawing, the continuous chemical nickel plating system there illustrated, and suitable for the carrying out of the present process, is essentially of the arrangement disclosed in the Talmey and Crehan patent. More particularly, the system fundamentally comprises a first reservoir 11a, a second reservoir 1lb, a plating tank or chamber 12, a condenser 13, a primary vacuum flash tank 14, a secondary vacuum ilash tank 15, a primary steam jet pum-p 16, a secondary steam jet pump 17, and a mechanical pump 13. The reservoir 11a includes a baffled storage compartment 19a and a communicating regeneration compartment 20a; while the reservoir 11b includes a baffled sto-rage compartment 19h and a communicating regeneration compartment 2Gb. In the arrangement, the inlet of the pump 18 selectively communicates with the upper and lower portions of the storage compartments 19a and 19h va respectively associated control valves 21a- 22a and 21h-22h; and the outlet of the pump 18 communicates with the upper portion of the condenser 13. The lower portion of the condenser 13 communicates with the upper portion of the plating tank 12; and the lower portion of the plating tank 12 communicates with the upper poriton of the primary vacuum dash tank 14. The lower portion of the primary vacuum flash tank 14 communicates with the upper portion of the secondary vacuum flash tank 16; and the lower portion of the secondary vacuum ash tank 15 selectively communicates with the upper portions of the regeneration compartments 25a and Zibb via respectively associated control Valves 23a and 23b. Also, the upper portion of the primary vacuum tiash tank 14 communicates with the primary steam jet pump 16, that is also connected to an associated source of high-pressure steam, not shown; and the discharge from the primary steam jet pump 16 communicates with the upper portion of the condenser 13. Also, the upper portion of the secondary vacuum ash tank 15 communicates with the secondary steam jet pump 17, that is also connected to the associated source of high-pressure steam, not shown; and the discharge from the secondary steam jet pump 17 communicates with the atmosphere. This system contains an aqueous chemical plating solution of the character previously described;` whereby'a first portion of the` plating solution is stored ir one of the reservoirs 11a or 11b at a relatively low temperature well below the boiling point thereof and in a relatively concentrated form; while a second portion of the plating solution is held as a bath in the plating tank or chamber 12 at a relatively high temperature slightly below the boiling point thereof and in a relatively dilute form.

In the operation of the system, the plating solution in the storage compartment 19a or 19b may have a temperature of about F.; while the plating solution in the plating tank 12 may have a temperature of about 210 F. The plating solution is circulated from the upper portion of the storage compartment 19a or 19b (depending upon which of the control valves 21a or 2lb occupies its open position) by the pump 18 into the upper portion of the condenser 13. wherein it is both heated to the required temperature of about 210 F. and diluted to the required concentration by the discharge from the primary steam jet pump 16. The dilution of the plating solution in the condenser 13 is achieved not only by the introduction of the steam thereinto, but also by the introduction of the water vapor thereinto that is withdrawn from the upper portion of the primary vacuum flash tank 14 by the primary steam jet pump 16. The plating solution from the condenser 13 is circulated into the plating tank 12 and thence into the upper portion of the primary vacuum tiash tank 14 and therefrom into the upper portion of the secondary vacuum ilash tank 15, and ultimately back into the upper portion of the regeneration compartment 26a or 20b (depending upon which of thecontrol valves 23a o-r 2312 occupies its open position). In the primary vacuum ash tank 14, a vacuum of about l2 Hg is drawn by the primary steam jet pump 16; whereby water vapor is withdrawn from the contained plating solution, as previously noted, so that the plating solution in the primary vacuum flash tank 14 is both concentrated and cooled prior to introduction into the secondary vacuum ash tank 15. In the secondary vacuum flash tank 15, a vacuum of about 22" Hg is drawn by the secondary steam jet pump 17; whereby water vapor is withdrawn from the contained plating solution, so that the plating solution in the secondary vacuum flash tank 15 is both further concentrated and cooled prior to the return thereof to the regeneration compartment 20a or 20h. The plating solution returned into the regeneration compartment 26a or 2Gb may have a temperature of about 150 F., as previously noted, as a consequence of the tandem cooling effects produced in the primary vacuum flash tank 14 and in the secondary vacuum tlash tank 15. Also, the plating solution thus returned to the regeneration compartment 20a or 20b is in the relatively concentrated form, as previously noted, as a consequence of the tandem concentrating effects produced in the primary vacuum flash tank 14 and in the secondary vacuum flash tank 15. Since the discharge of the secondary steam jet pump 17 is to the atmosphere, the water vapor withdrawn from the plating solution in the upper portion of the secondary vacuum flash tank 15 prevents the build-up of water in the circulated plating solution; and preferably, the weight of the steam introduced into the plating solution in the condenser 13 by the primary steam jet pump 16 substantially equals the Y thereof; and the'bodies -are withdrawn from the plating bath when the coatings thereon are of the desired thickness. Incident to the plating of the nickel upon the catalytic bodies, the initial composition of the plating bath is altered by the reduction of the nickel cations and the oxidation of the hypophosphite anions, as previously noted, and the initial pH of the bath is reduced, as previously explained; whereby it is necessary to regenerate the-plating solution in the regeneration compartment 20a or 20b by the addition thereto of an alkalizing reagent to restore the initial pH thereof and-of a soluble nickel salt and a soluble hypophosphite to restore the initial cornposition thereof with respect to nickel cations and hypophosphite anions, the reagents mentioned being supplied into the regeneration compartment 20a or 2Gb, and being thoroughly dissolved and mixed thereinto before circulation back-into thecommunicating storage compartment 19a or 1911.

Further, the system comprises make-up equipment 36 that may include live tanks 31 to 35, inclusive, that selectively communicate with make-up conduits 36 and 37 communicating with the regeneration compartments 20a and Ztlb. More particularly, the tanks 31 to 35, inclusive, may be selectively connected to the conduit 36 via respective control valves 41 to d5, inclusive, and the tanks 31 to 35, inclusive, may be selectively connected to the conduit '3? via respective controlvalves 51 to 55, inclusive. As a matter of convenience, the added alkalizing reagent maybe derived from an aqueous so-dium hydroxide stock solution stored in the tank 31, the added nicked reagent may be derived from an aqueous nickel sulfate stock solution stored in the tank 32, the added hypophosphite reagent may be derived from an aqueous sodium hypophosphite'stock solution stored in the tank 33, water may be'stored in the tank Se, and an aqueous sulfuric acid stock solution may be stored in the tank 35. It Will be understood that the valves 41, ft2, 43 and 44 are appropriately manipulated in order to bring about the required addition of the reagents from the tanks 31, 32, 33 and 34 into the regeneration compartment 20a, while the valves 51, 52, 53 and 54 are appropriately manipulated in order to bring about the required addition of the reagents from the tanks 31, 32, 33 and 34 into the regeneration compartment 2Gb.

Finally, the system comprises apparatus 60 that is employed, as explained more fully hereinafter, for the removal of phosphite and other ions, the inlet to the apparatus atl being selectively connected to the lower portion of the secondary vacuum flash tank via an associated control valve 61, and the outlet from the apparatus 6-1) being selectively connected to the regeneration compartments a and 2Gb via respective control valves 62a and 62h.

Asa matter of operating procedure, the plating solution may be continuously circulated from one of the reservoirs (for example, the reservoir 11a) to the plating tank 21 and back to the one reservoir 11a; and the plating solution may be continuously regenerated in the regeneration compartment Ztln by the continuous addition of the reagents thereto by proper manipulation of the control valves 41, 42, t3 and 44. Of course, this regeneration of the plating solution only restores the composition thereof with respect to nickel cations, hypophosphite anions and pH, but does not restore the initial composition thereof with respect to the ions that are built-up therein, both bythe plating reactions and by the additions of the reagents mentioned. ln other words, as the plating solution is used in the plating operation, phosphite anions build-up therein, and likewise in the supply of make-up reagents thereto both sodium cations and sulfate anions are built-up therein (assuming that the stock solutions employed comprise nickel sulfate and sodium hypophosphite, as previouslyrmentioned).

Accordingly, after'predetermined utilization of the plating solution in the continuous plating system and continuous-regeneration thereof with respect to the supply of make-up reagents thereto, it is necessary to effect a regeneration of the plating solution by the utilization of the apparatus 6@ so as to bring about the removal from the plating lsolution ofthe phosphite anions, as Well as the sodiurncations andthe sulfate anions. At this time, the control valve 23a is closed and the control valves 61 and 62h are opened, and operation of the apparatus 69 is initiated, as explained more fully hereinafter; whereby the plating solutionfrom the lower portion of the secondary vacuum flash tank 15 is circulated through the apparatus 6i) and'thence into the regeneration compartment 2Gb of the reservoir 11b. At this time, the control valves 52, 53, 54 and 55 are appropriately controlled in order to cause the supply of the required make-up reagents into the regeneration compartment 20h so as substantially completely to restore the initial composition of the chemical plating solution. In order to accommodate the complete removal of the depleted plating solution from the reservoir 11a, the control valve 22a is opened to place the lower portion or" the reservoir 11a into communication withthe inlet of the pump 18.

In view of the foregoing, it 4Will be understood that the depleted plating solution is circulated from the reservoir 11n through the plating tank 12 and thence into the apparatus 60 and then into the reservoir 11b. Subsequently the restored plating solution is circulated from the reservoir 11b throughthe plating tank 12 and thence back into the regeneration compartment 2Gb of the reservoir 11b, the control valves 61, 23a and 22h being operated into their closed positions and the control valves 23b and 2lb being operated into'their open positions at this time, whereby operation of the apparatus 60 may be arrested.

ln View of the foregoing description of the mode of operation of the continuous plating system, it will be understood that as the plating solution is circulated from the reservoir 11a through the plating chamber 12, it is continuously regenerated by the addition thereto of nickel cations, hypophosphite anions and hydroxyl anions, employing the make-up equipment 30; and after a predetermined utilization thereof, it becomes necessaryto regenerate it by the removal therefrom of phosphite anions, sodium cations and sulfate anions, employing the apparatus 6%, followed by the addition thereto of nickel cations, hypophosphite anions and hydrogen cations, employing the make-up equipment 30. This predetermined utilization and consequent depletion of the plating solution is manifest by the build-up therein of a phosphite anion concentration Within the approximate range 0.7 to 1.5 m. p. l., and is normally reached when the accumulative nickel salt addition is such that about 400% to 500% nickel cations (with respect to the initial nickel cation content of the plating solution) have been added thereto in the continuous regeneration thereof, employing the makeup equipment 30. i

Considering now in greater detail the matter of the removal of the phosphite anions, together With the sodium cations and the sulfate anions, from a depleted plating bath in the apparatus 60, it is first noted that the desirable values contained in the depleted plating bath are recovered and the resulting aqueous solution is reconstituted to provide the restored plating solution. Specifically, the pH of the depleted plating bath is first adjusted to 3.0 with sulfuric acid, and then an aqueous slurry of ferric sulfate is added thereto in order to bring about the conjoint precipitation of ferrie phosphite and ferrie hypophosphite; which lcomposite precipitate is removed by filtration in a Filter Cake l, producing a Filtrate I containing substantially all of the nickel-and sodium cations, substantially all of the sulfate and organic anions and small amounts of the phosphite and hypophosphite anions, as illustrated in the following ow sheet:

Flow sheet I Depleted bath IIIB Filtrate I Adiust pH Ni+ .....--..0.08 in. p. l. to 3.0 with NaHzP Oz 0.022 m. p. l. .p. HZSOi; add NatHPO .129 m.p.l. Lactxe acid....0riginal FMS 0.,);1, N azS O4... Some. Succinic Lactic acid --A1l of acid. Original original. i Succinic acd.90% of original.

Filter cake I FezP a)a F ez(HtP 0:4)3

To Filtrate I thus produced, there is added an aqueous slurry of barium hydroxide in order to precipitate barium sulfate; which precipitate is removed by filtration in a Filter cake II, producing a Filtrate II containing substantially all of the nickel cations, some of the sodium cations, small amounts of the phosphite and hypophosphite anions, some of the sulfate anions and substantially all of the organic anions, as illustrated in the following ow sheet:

Flow sheet II Add: Filtrate II Filtrate I Ba(OH)2 (above) Ni++ ..0.08 m. p. l

NaHzPOz..- -..-0022 m. p. 1 NazHPOg --..0129 m. p.1 NazSOi..." Some. Lactic acid.. .All of original. Succinic acie- 90% o original.

Filter cake II l BaSOa Filtrate II thus produced is then cooled to a relatively low temperature, about 0 to 5 C., while bubbling therethrough a small amount of gaseous carbon dioxide throughout a time interval of about 30 minutes in order to precipitate sodium sulfate and some sodium carbonate and sodium bicarbonate; which precipitates are removed by filtration in a Filter cake III, producing a Filtrate III containing substantially all of the nickel cations, small amounts of the sodium cations, small amounts of the phosphite anions, hypophosphite anions and sulfate anions and substantially all of the organic anions, as illustrated Filtrate III thus produced is employed as the base of a restored plating solution, since it contains the desired values of nickel cations and organic anions; and specifically Filtrate III is reconstituted by the addition thereto of the required small amount of nickel sulfate and the re- `quired ,larger amount of sodium hypophosphite, together with required pH adjustment to the initial value of about 4.6, utilizing H2504 and NaOH as required, so as to provide the restored plating bath of the required composition.

In the treatment, the pH of the depleted Bath IIIB is firstadjusted to about 3.0 with sulfuric acid priorto the addition of the ferrie sulfate, so as to bring about the conjoint precipitation of ferrie phosphite and ferrie hypophosphite. Subsequently, the excess sulfate anions are removed from Filtrate I by the reaction with barium hydroxide, precipitating barium sulfate. Ultimately, most of the sodium cations are removed from Filtrate II by the cooling and the reaction with gaseous carbon dioxide, precipitating conjointly sodium sulfate, sodium carbonate and sodium bicarbonate.

In view of the foregoing, it will be understood that in the continuous chemical nickel plating process, the effective or useful life of the initial plating solution may be greatly extended by the regeneration thereof, including the removal of the undesirable phosphite anions, sodium cations and sulfate anions therefrom, without the introduction thereinto of foreign ions, whereby the plating solution may be restored any number of times after a corresponding number of intervening depletions thereof.

In the foregoing description, periodic or intermittent regeneration of the plating solution, with respect to the removal of sodium cations, phosphite anions and sulfate anions, in the continuous plating system was explained; however, it will be understood that this regeneration of the plating solution in the system may be continuous. This may be accomplished in a ready manner by opening the control valves 61 and 62a (utilizing the reservoir 11a) so that the apparatus 60 is arranged in bypassing relation with respect to the direct return of the plating solution to the regeneration compartment 20a, the control valve 23a also being open at this time. Thus in the arrangement, two portions of the plating solution from the lower portion of the secondary vacuum flash tank 15 respectively flow directly into the regeneration compartment 20a viathe control valve 23a and indirectly into the regeneration compartment 20a via the control valve 61 and the apparatus 60. By treatment of the portion of the plating solution passing through the apparatus 60, in the manner previously explained, the required removal of phosphite anions, sodium cations and sulfate anions may be accomplished upon a continuous basis so as to prevent excessive depletion thereof in the continuous plating operation.

Accordingly, it will be understood that there has been provided a continuous chemical nickel plating process that is highly suitable for use on an industrial scale, that involves regeneration of the plating bath, as it becomes depleted with use, in a simple manner, thereby rendering the plating bath of exceedingly long life and contributing to overall efficiency of the continuous chemical nickel plating process.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. The continuous process of chemically plating with nickel a body essentially comprising an element selected v from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum; which comprises providing an aqueous plating solution of the nickel cation-hypophosphite anion type and having an initial composition including a pH in a first given range from about 4 to about 7 and a nickel cation concentration in a second given range and a hypophosphite anion concentration in a third given range; holding a portion of said solution in a plating chamber at a plating temperature disposed below the boiling point thereof but well above room temperature; immersing said body in the portion of said solution in said plating chamber to etfect nickel plating on the surface thereof; withdrawing said 11 body from the portion of said solution in said plating chamber after a time interval corresponding to the thickness of the nickel plating on the surface of said body that is desired; said nickel plating of said body resulting from the reduction of nickel cations to metallic nickel with the corresponding oxidation of hypophosphite anions to phosphite anions, whereby during said time interval both nickel cations and hypophosphite anions are depleted and both hydrogen cations and phosphite anions are produced in the portion of said solution in said plating chamber, with the result that the portion of said solution in said plating chamber tends to depart substantially from said initial composition; withdrawing during said time interval a part of said solution from said plating chamber; treating during said time interval the withdrawn part of said solution to restore the same substantially to said initial composition; said treatment of the withdrawn part of said solution including removing therefrom by precipitation as ferric hypophosphite a major fraction'of the contained hypophosphite anions and removing therefrom by precipitation as ferric phosphite a major fraction of the contained phosphite anions, without removing therefrom any more than a minor fraction of the contained nickel cations and without introducing thereinto any substantial foreign ions, followed by adding thereto sui`n`cient hydroxyl anions to restore the pH thereof -into said first range and suicient nickel cations to restore the concentration thereof into said second range and'sufiicient hypophosphite anions to restore the concentration thereof into said third range; and returning during said time interval a portion of the restored part of said solution into said plating chamber.

2. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions and a given organic additive to produce a restored aqueous chemical nickel plating solution containing predetermined nickel cations and predetermined hypophosphite anions and only some. phosphite anions and substantially said given'organic additive and having a givenpH within the approximate range 4 to 7, which comprises removing from said depleted solution by precipitation as ferric hypophosphite a major fraction of the contained hypophosphite anions and removing from said depleted solution by precipitation as ferric phosphite a major fraction of the contained phosphite anions, without removing therefrom any more than a-minor fraction of the contained nickel cations or any more than a minor fraction of the contained organic additive and without introducing thereinto any substantial foreign ions, whereby the resulting solution contains only some hypophosphite anions and some phosphite anions and substantial nickel cations and substantially said given organic additive, :and adding to the resulting solution suiicient nickel cations to obtain said predetermined nickel cations therein and suicient hypophosphite anions to obtain said predetermined hypophosphite anions therein and sufficient pH control ions to obtain said given pH thereof.

3. The process of regenerating a depleted aqueous chemical nickel plating solution Vcontaining substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to pro-duce a restored aqueous chemical Vnickel plating solution containing predetermined nickel cations and predetermined hypophosphite anions and only somephosphite anions and having a given pH, which comprises adjusting the pH of said depleted solution toa value at least as low as 3, reacting the resuiting solution with ferrie sulfate to precipitate both ferr-ic hypophosphitc and fcriic phosphite therein, removing the precipitated ferrie hypophosphite and ferric phosphite from the reacted solution, reacting the 'then resulting solution with barium hydroxide to precipitate barium sulfate therein, removing the precipitated barium sulfate from the reacted solution, and adding to the then resulting solution sufficient soluble nickel salt to obtain said predetermined nickel cations therein and suicient soluble hypophosphite to obtain said predetermined hypophosphite anions therein and 'suicient pH control ions to obtain said given pH thereof.

4. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypo-phosphite anions and considerable phosphite anio-ns and some sulfate anions to produce a restored aqueous chemical nickel plating solution containing predetermined nickel cations and predetermined hypo-phosphite anions vand only some phosphite anions and some sulfate anions and having a given pH, which comprises adjusting with sulfuric acid the pH of said depleted solution to about 3, reacting the resultingrsolution with ferric sulfate to precipitate both ferric hypo-phosphite and ferrie phosphite therein, removing the precipitated ferric hypophosphite and ferrie phosphite from the yreacted solution, reacting the then resulting solution with barium hydroxide to precipitate barium sulfate therein, removing the precipitated barium sulfate-from thereacted solution, and adding to the then resulting solution suflicient soluble nickel salt to obtain said predetermined nickel cations Vtherein and suicient soluble hypophosphite to obtain said predetermined hypophosphite anions therein and suthcient pH control ions to obtain said given pH thereof.

5. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions and given lactic anions to produce a restored aqueous chemical nickel plating solution containing predetermined nickel cations and predetermined hypophosphite anions and only some phosphite anions and substantially said given lactic anions and having a given pH, which comprises adjusting the pH of said depleted solution to a value at least as low as 3, reacting the Vresulting solution with ferric sulfate to precipitate both ferric hypophosphite and ferric phosphite therein, removing the precipitated ferric hypophosphite and ferric phosphite from the reacted solution, reacting the then resulting solution with barium hydroxide to precipitate barium sulfate therein, removing the precipitated barium sulfate from the reacted solution, and adding to the then resuiting solution suflieient soluble nickel sait to obtain said predetermined nickel cations therein and sufficient soluble hypophosphite to obtain said predetermined hypophosphite anions therein and sufficient pH control ions to obtain said given pH thereof, whereby said restored solution thus produced contains substantially said given lactic anions of said depleted solution.

6.*The process of treating a depleted chemical nickel plating solution of the nickel cation-hypophosphite anion type to remove phosphite anions therefrom, said process comprising adjusting the pH of said depleted solution to a value at least as low as 3, reacting the resulting solution with ferrie sulfate to precipitate ferrie phosphite therein, and then separating the precipitated ferric phosphite from the then resulting solution.

7. The process set forth in claim 6, and further com prising reacting the then resulting solution with barium hydroxide to precipitate barium sulfate therein, and then separating the precipitated barium sulfate from the then resulting solution.

References Cited in the le of this patent UNlTED STATES PATENTS 

1. THE CONTINUOUS PROCESS OF CHEMICALLY PLATING WITH NICKEL A BODY ESSENTIALLY COMPRISING AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF IRON, COBALT, NICKEL, ALUMINUM, COPPER, SILVER, GOLD, PALLADIUM AND PLATINUM; WHICH COMPRISES PROVIDING AN AQUEOUS PLATING SOLUTION OF THE NICKEL CATION-HYPOPHOSPHITE ANION TYPE AND HAVING AN INITIAL COMPOSITION INCLUDING A PH IN A FIRST GIVEN RANGE FROM ABOUT 4 TO ABOUT 7 AND A NICKEL CATION CONCENTRATION IN A SECOND GIVEN RANGE AND A HYPOPHOSPHITE ANION CONCENTRATION IN A THIRD GIVEN RANGE; HOLDING A PORTION OF SAID SOLUTION IN A PLATING CHAMBER AT A PLATING TEMPERATURE DISPOSED BELOW THE BOILING POINT THEREOF BUT WELL ABOVE ROOM TEMPERATURE; IMMERSING SAID BODY IN THE PORTION OF SAID SOLUTION IN SAID PLATING CHAMBER TO EFFECT NICKEL PLATING ON THE SURFACE THEREOF; WITHDRAWING SAID BODY FROM THE PORTION OF SAID SOLUTION IN SAID PLATING CHAMBER AFTER A TIME INTERVAL CORRESPONDING TO THE THICKNESS OF THE NICKEL PLATING ON THE SURFACE OF SAID BODY THAT IS DESIRED; SAID NICKEL PLATING OF SAID BODY RESULTING FROM THE REDUCTION OF NICKEL CATIONS TO METALLIC NICKEL WITH THE CORRESPONDING OXIDATION OF HYPOPHOSPHITE ANIONS TO PHOSPHITE ANIONS, WHEREBY DURING SAID TIME INTERVAL BOTH NICKEL CATIONS AND HYPOPHOSPHITE ANIONS ARE DEPLETED AND BOTH HYDROGEN CATIONS AND PHOSPHITE ANIONS ARE PRODUCED IN THE PORTION OF SAID SOLUTION IN SAID PLATING CHAMBER, WITH THE RESULT THAT THE PORTION OF SAID SOLUTION IN SAID PLATING CHAMBER TENDS TO DEPART SUBSTANTIALLY FROM SAID INITIAL COMPOSITION; WITHDRAWING DURING SAID TIME INTERVAL A PART OF SAID SOLUTION FROM SAID PLATING CHAMBER; TREATING DURING SAID TIME INTERVAL THE WITHDRAWN PART OF SAID SOLUTION TO RESTORE THE SAME SUBSTANTIALLY TO SAID INITIAL COMPOSITION; SAID TREATMENT OF THE WITHDRAWN PART OF SAID SOLUTION INCLUDING REMOVING THEREFROM BY PRECIPITATION AS FERRIC HYPOPHOSPHITE A MAJOR FRACTION OF THE CONTAINED HYPOPHOSPHITE ANIONS AND REMOVING THEREFROM BY PRECIPITATION AS FERRIC PHOSPHITE A MAJOR FRACTION OF THE CONTAINED PHOSPHITE ANIONS, WITHOUT REMOVING THEREFROM ANY MORE THAN A MINOR FRACTION OF THE CONTAINED NICKEL CATIONS AND WITHOUT INTRODUCING THEREINTO ANY SUBSTANTIAL FOREIGN IONS, FOLLOWED BY ADDING THERETO SUFFICIENT HYDROXYL ANIONS TO RESTORE THE PH THEREOF INTO SAID FIRST RANG AND SUFFICIENT NICKEL CATIONS TO RESTORE SAID FIRST RANGE AND SUFFICIENT NICKEL CATIONS TO RESTORE FICIENT HYPOPHOSPHITE ANIONS TO RESTORE THE CONCENTRATION THEREOF INTO SAID THIRD RANGE; AND RETURNING DURING SAID TIME INTERVAL A PORTION OF THE RESTORED PART OF SAID SOLUTION INTO SAID PLATING CHAMBER. 